Based on the inheritable traits which chemical carcinogens induce in living cells and recent knowledge that these compounds alter gene expression, a direct action on the chromosomal material is suspect. This proposal is concerned with the analysis of the interaction of carcinogenic polycyclic aromatic hydrocarbons (PAH) with nuclear chromatin in an in vitro system (cloned lines of mouse embryo cells). The carcinogenic PAH have been shown to trigger malignant transformation in these cells. A high affinity, saturable class of binding sites has been localized in a transcriptionally active nuclear fraction (Fraction 1). Our results show that this localization in Fraction 1 is much greater for the more potent PAH compared to the weak or noncarcinogenic PAH. There are two types of binding in Fraction 1: A weak binding, extractable with organic solvents and referred to as "noncovalent" binding, and a strong binding, which is nonextractable and referred to as "covalent" binding. The "covalent" binding to this specific nuclear subfraction is a metabolic dependent process whereas the "noncovalent" binding is not. Our recent evidence suggests that only carcinogenic PAH and not the non- or weakly-carcinogenic PAH display the marked noncovalent as well as "covalent" binding to Fraction 1. It is proposed to further characterize this class of binding sites with respect to 1) its specificity for additional carcinogenic and noncarcinogenic compounds, 2) the nature of the chromatin component which is bound (e.g., DNA protein, or RNA), and possibly the chemical identity of some of the components and, finally, 3) to establish a cell-free binding system which mimics the patterns of binding observed in the whole cell system; to use this cell-free system to assesss the role of cytosol receptor proteins which carry the (3H)PAH or its metabolites to the nucleus and to assess, by competitive binding assays, the specificity of the Fraction 1 binding sites for the various (3H)PAH ligands. Time permitting, in cases of highly specific sites localized on certain macromolecules, analysis of the amino acid of nucleotide bound as well as the species of PAH bound will be investigated. (Text Abridged.)